R6 shock conversion questions

[Sooty]

This is my first post on the forum and I’d just like to say thanks for all the excellent information, hints and tips that everybody here contributes. You have saved me a lot of time and effort finding out the hard way.
I’ve just returned to motorcycling after a 25 year break known as a mortgage, ex-wife and three kids. Last summer I spotted a 1994 FZR600 American import in the paper with only 6000 miles on the clock from new, right sort of money, all original and in pretty good nick. I’m the third owner the first being an elderly gentleman that judging by the tyre wear only went in straight lines. The second was a student with two bikes and not enough money to run 2 on the road. He had owned the bike for three years and had only added a 1000 miles on it since he’d bought it and not done anything to it other than a service and remove the decals from the fairing and tank. He had bought the bike through a friend of a friend as the elderly gentleman was deemed unfit to be on the road on a bike. Kept getting lost and unable to find his way home I believe.
The first job after a thorough service and inspection of essentials was to put some new rubber on her. Fitted I can’t remember now but it had a cross ply on the front and a radial rear. Being limited to what I can get for an 18 inch rear and not really wanting to put my knee on the tarmac for every roundabout I decided to go for Avons recommendation which was their sports tourer Storm2 tyres. They recommended 150/70 rear 110/70 front.
I know this is long winded but to get to my point I’ve decided to upgrade the rear shock with the R6 conversion that is well documented on here. I managed to find a brand new R6 shock 08/10 flavour from a race prep shop on flea bay for £60 ($95 approx) including freight; obviously they were prepping bikes for the track and upgrading the suspension. They are asking more than that for well used units in the UK so I think I got a good deal.
Now here is my dilemma, the original fitment tyres would have been 110/70 front 140/60 rear. New rubber front is the same as original but the rear is a larger diameter as well as a wider tyre. I was trying to work out what dog bone length I would need. I didn’t realise how much higher the rear is till I did some poking around for information on the internet. The only tyre I could find that is made in the original fitment size and gave diameter was the Shinko Podium range. This gave a diameter of 625mm for a new tyre. Avon quote 667.2mm diameter for the 150/70, simple maths tells me that my rear has 42mm larger diameter than original fitment giving me a ride height increase of 21mm. Part of the reason for doing the R6 shock conversion was I did not think the bike handled as well as its reputation.
Two questions, one is does anybody know what the correct original ride height is at a datum point on the frame? The second is if my tyre dimensions are correct to return the bike to its original ride height based on the information I got for the tyre sizes I should need dog bones with 147mm centres which I believe is the standard length. Am I right in this presumption

[yamaha_george]

Sooty,
we have no way of knowing where in the world you are, so recommending a source is a tad difficult. American models vary by year to European models and in the case of the 600 there is a 1year lag in model identification.
My UK 92 is an American '91 so you see the problem .................

Please put your location in your personal profile and we just might be able top clear this up for you.

[Sooty]

I'm in Manchester Uk. The bike is UK registered '95 but manufactured '94.

Editted by Y_G

Sorry got that wrong - Manufactured '95 (3HHE) registered in UK '96

[fzrbrandon]

I should need dog bones with 147mm centres which I believe is the standard length. Am I right in this presumption

The standard dogbone length is actually 148mm. What you COULD do is get a set of Reelrazor's adjustable dogbones. That would probably save you a lot of headache trying to figure out the exact "proper" length for any given rear tire.

Hope that helps

[jdugen]

Hi Sooty
I'm in Manchester too, just finished a complete re-build on a '91 wreck.
Pity you have shelled out for a tyre as there is, in the UK, a cheap and easy way to 17'' rear heaven. The TDM 850 wheel goes in with a minimum of modification, all parts interchangable.
The ability to post photos on this site eludes me at the moment but I have the mod documented if you want to e-mail me.

Cheers

[yamaha_george]

I'm in Manchester Uk. The bike is UK registered '95 but manufactured '94.

Editted by Y_G

Sorry got that wrong - Manufactured '95 (3HHE) registered in UK '96

Sooty,
Nice to have another Brit on the board.As has been said else where ReelRazor is the man to get the adjustable Dog Bones from.

A lot of guys have them to do their rear end swaps etc.

If you are set on having "standard" looking ones then I have a set of RR's Dog Bones I can loan you to set up the bike (as I did ) and then get a custom set of "standard looking ones" made specifically for you & your bike.

Before you get into laying out money and working blind I suggest you read the sections in the WIKI on suspension setting etc there also may be references in Gear Head & Guru section

[rotortech]

+ 1 to Reelrazor's adjustable dogbones. I put them on last season and I am still going to tweak them a bit this summer. When I get the handling sorted out I will have some stockish looking dogbones made to install. Not that there is anything wrong with the way the adjustable ones look. Just finishing the job.

[Sooty]

The reasons for my questions is that everyone has a different riding style and weight, this could be because of their size or whether they are carrying luggage or two up. I would like to return the bike as close to the original ride height as possible before trying to get the best to suite me. Yamaha obviously spent a lot of time, money and effort to hit a happy medium and would be a good starting point. With the ride height being plus from the original (by my calculations) it is not something that Yamaha expected when designing the bike. I’ve thought about a 17” rear wheel conversion but the easy one using the 850 wheels would mean that the rims would not match and I think I’m right in thinking that the front end for the 850 sported a 18” rim, back to the problems of tyre choice and steering head geometry.
From the forum I have found dog bone length increases/decreases the height 2.4mm for every 1mm lost or gained on the bone length. The shorter the bones the higher the ride height, longer for lower. For the conversion to bring back standard ride height (R6 shocks are shorter, therefore lowers the height) members are quoting a length of 138mm, I’m presuming on standard tyres? Working on my bike being 21mm higher than stock would equate to lengthening the bone from 138mm to 146.75mm, which is nearly standard bone length. Yamaha obviously think that ride height will decrease from static with load and the suspension working therefore increasing the angle of the steering head. At present I’m starting with a more acute steering angle because the back end is higher which could account for the front feeling a little skittish in a corner.
Not knowing the original ride height and never really rode the bike with the tyres it came with as they were of unknown age (remember she was already 15 when I bought her), mixed types and the centre tread on the rear well squared off I’m stuck for a starting point. I’ve thought of the adjustable bones but they will not give me a starting point and may run out of adjustment as they are designed to shorten rather than lengthen. As I’m not intending to use the bike for track days only road and then not at silly speeds. I just want the bike to give me the confidence that I can push her a little harder when required without any unknown surprises.

[rotortech]

Sooty,

I respect your diligence in trying to find the correct ride height for your bike. Even from Yamaha, it is only correct for one rider - not for everyone else. You have already started to diagnose the handling by your comment on the twitchy steering. I believe the adjustable dog bones will have enough adjustment to handle the situation. Reelrazor would have a better idea of that. I suspect that trying to determine the exact length and having a fixed dogbone made will probably get you closer to what you want, but not exactly. There are just too many variables.

Take Yamaha-George's generous offer to loan you his adjustable dogbones. Once you know the right length, you can have the fixed ones made up.

[yamaha_george]

Guys,
I think Sooty is looking for the "static" ride height of the original 600 i.e. being held upright but with no rider on the bike to some point from ground to a VERY specific place on all our bikes such as the bottom of the rear pegs metal loop. or some other easily reachable place.

I would help here but my bike has a non - stock swing arm Tri-block & shock albeit with the original 18" wheel.

[DonTZ125]

IMHO, the stock ride height is utterly irrelevant - it is a starting point. You have a starting point right now with what you have. If you are planning to modify your ride height for improved handling then replace the tires, refurbish the suspension, and start your checks and measurements from what you have.

Really - if you are going to wind up at point 'C', does it really matter if you start from point 'A' or point 'E'?

[fzrbrandon]

FWIW, Yamaha's stated stock seat height is 30.9". I'm guessing that measurement was taken with the preload set to the center position...

[reelrazor]

Or, you could take the posted rake angle and try to duplicate it using an angle finder on the fork leg

http://www.harborfreight.com/dial-gauge ... 34214.html

It is a good item to have to monitor changes. Can also use it to look at swingarm angle, etc.

[jdugen]

It took me one hour from offering up the TDM wheel, doing a few measurments, a bit of cutting and grinding to having the wheel mounted and running true.
The 'rim' design is slighlty different in theat there are hollows at the bottom of the spokes. They look perfectly in keeping with the front wheel.
The tyre diameter of a 5'' x 17'' is almost the same, I had no noticable drop in saddle height.
The fact that you are riding UK's overpoliced, potholed third world roads means an expensive shock upgrade is more for looks than actual improvement, wait until you have ridden it, you might be pleasantly surprised (I was). This, of course, is given that the shock has not leaked its guts out and that you have changed front fork oil for 15W. I have managed to post a photo in my gallery.
P.S. Can someone PLEASE tell me how to put a photo into a post on this forum. All I get when I try is some square brackets and IMG?

[Sooty]

Many thanks for everybody’s hints, tips and advice. I hope to do my conversion this weekend or at least make a start. I’ve just got to open up the bush on the new shock to 12mm so it will take the top mounting bolt. The spacers I’m cheating on as stainless A4 M12 “form A” washers are 2.5mm thick off the shelf, two each side should take up the slack. I’ve also taken “reelrazors” advice and ordered an inclinometer similar to the one he pointed me at to check out the castor angle. Yamaha quote a castor angle of 25 degrees and trail of 94mm in their manual. I’ll report back on my findings. Yamaha George many thanks, I may take up your kind offer of the loan of your adjustable dog bones if my calculations are wrong.

For those of you in the UK you might like to know a source for non standard dog bones you can try here http://www.cjaccessories.co.uk mail order only, I can’t see if the offer overseas shipping but they were very helpful when I enquired. They can supply jack up/lowering kits for many popular bikes current and not so new.